1/2 cup ponzu
1/4 cup orange juice
1 tsp honey
2 cloves garlic, roughly chopped
1 Tbsp rice vinegar
1 Tbsp canola or vegetable oil
1 pinch fresh black pepper
2 lb flank steak, trimmed of any excess fat
Combine first 7 ingredients in a bowl and whisk until thoroughly mixed. Taste, and adjust seasoning if necessary with more honey or vinegar.
Place the steak in a large ziploc bag, and pour in the ponzu mixture. Seal the bag and refrigerate for 4 hours or overnight.
When you're ready to cook, heat your grill (or broiler) to high. While the grill is heating, remove the meat from the refrigerator and let it come to room temperature. Cook for 4 minutes on each side, brushing occasionally with the leftover marinade. Remove the meat from the grill and allow it to sit, covered with a piece of aluminum foil, for 10-15 minutes before slicing.
You can make this dish far ahead; it's just as good cold as hot.